T. Mateus* and A. C. Oliveira

New Energy Tec. Unit, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto,

Portugal

* Corresponding Author, tiagomateus@engenheiros. pt
Abstract

The use of solar energy for cooling is an attractive concept, because the need of cooling happens at the same time of solar radiation availability. Three computational models were developed in TRNSYS for three different buildings: office, hotel and single-family house. The models allow the simulation of solar cooling systems with flat plate collectors or vacuum tubes, with a gas boiler or electrical compression chiller backup. Lisbon, Rome and Berlin were the locations studied. The TRNSYS models are able to run for a whole year (365 days), according to control rules (self-deciding whether to operate in heating or cooling modes), with the possibility of combining cooling, heating and DHW applications. These user friendly models allowed to perform an exhaustive study about the economic viability of solar cooling systems.

Keywords: solar thermal system, solar cooling, heat pump, absorption chiller

1. Introduction

Solar thermal cooling systems are still in their infancy regarding practical applications. A survey done by the European Solar Thermal Industry Federation [1], showed that in 2006 there were only about 100 solar cooling systems installed in Europe. Of those, about 67% where based on absorption cooling technology, and more than half used flat-plate solar collectors. The number of solar cooling systems will increase significantly in the near future, due to the arrival of new players to the market. There are today several absorption chillers driven by hot water available on the market, starting at a cooling capacity of about 4 kW. This makes it possible to install solar absorption cooling systems for several building sizes, from single-family residential to large commercial buildings.

However, for these applications to be economically interesting, namely to decrease their payback period, it would be important to extend the system operation period as much as possible throughout the year. Solar thermal collectors can also be used for water or indoor space heating, thus making it possible to use an integrated system for building cooling and heating.

This study aims to evaluate the potential of integrated solar absorption cooling and heating systems for building applications. The TRNSYS software tool [2], was used as a basis for assessment. Different building types were considered: residential, office and hotel. Three different locations and climates were considered: Berlin (Germany), Lisbon (Portugal), and Rome (Italy). The different local costs for energy (gas, electricity and water) were taken into account — see Table 1. Both energy and economic results are presented for all cases. Savings in CO2 emissions were also assessed for all cases.

to 10th October, Lisbon — Portugal *